Mallard

Mallard
A drake, hen, and their ducklings swimming
Conservation status

Least Concern (IUCN 3.1)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Subfamily: Anatinae
Genus: Anas
Species: A. platyrhynchos
Binomial name
Anas platyrhynchos
Linnaeus, 1758
Subspecies

See Mexican Duck, Anas and below

  • A. p. domesticus
    Domesticated duck   (Linnaeus, 1758)
Synonyms

Anas boschas

The Mallard, or Wild duck (Anas platyrhynchos[1]), probably the best-known and most recognizable of all ducks, is a dabbling duck which breeds throughout the temperate and sub-tropical America, Europe, Asia, New Zealand (where it is currently the most common duck species), and Australia.

The male birds have a bright green head, while the female's is light brown. The mallard lives in wetlands, eats water plants, and is gregarious. It is also migratory. The mallard is the ancestor of all domestic ducks, and can interbreed with other species of genus Anas.[2] This interbreeding is causing rarer species of ducks to become genetically diluted.

Contents

Characteristics

Male (right) and female (left) out of water

The mallard is 56–65 cm long, has a wingspan of 81–98 cm, and weighs 0.9–1.2 kg. The breeding male is unmistakable, with a bright green head, black rear end and a yellowish orange (can also contain some red) bill tipped with black (as opposed to the dark brown bill in females). The female mallard is light brown, like most female dabbling ducks. However, both the female and male mallards have distinct purple speculum edged with white, prominent in flight or at rest (though temporarily shedded during the annual summer moult). In non-breeding (eclipse) plumage the drake becomes drab, looking more like the female, but still distinguishable by its yellow bill and reddish breast.

In captivity, domestic ducks come in wild-type plumages, white, and other colours. Most of these colour variants are also known in domestic mallards not bred as livestock, but kept as pets, aviary birds, etc., where they are rare but increasing in availability.

A noisy species, the male has a nasal call, the female has a "quack" stereotypically associated with ducks.[3]

The mallard is a rare example of both Allen's Rule and Bergmann's Rule in birds. Bergmann's Rule, which states that polar forms tend to be larger than related ones from warmer climates, has numerous examples in birds. Allen's Rule says that appendages like ears tend to be smaller in polar forms to minimize heat loss, and larger in tropical and desert equivalents to facilitate heat diffusion, and that the polar taxa are stockier overall. Examples of this rule in birds are rare, as they lack external ears. However, the bill of ducks is very well supplied with blood vessels and is vulnerable to cold.

Behaviour

Bird with wings forward. Yellow bill, green head with white collar, brown body with blue wing feathers and orange feet.
Drake in flight

The mallard inhabits most wetlands, including parks, small ponds and rivers, and usually feeds by dabbling for plant food or grazing; there are reports of it eating frogs. It usually nests on a river bank, but not always near water. It is highly gregarious outside of the breeding season and will form large flocks, which are known as a sord.[4]

Female landing

It is strongly migratory in the northern parts of its breeding range, and winters farther south. For example, in North America it winters south to Mexico, but also regularly strays into Central America and the Caribbean between September and May.[5]

Reproduction

Mallards usually form pairs only until the female lays eggs, at which time she is left by the male. The clutch is 8–13 eggs, which are incubated for 27–28 days to hatching with 50–60 days to fledgling. The ducklings are precocial, and can swim and feed themselves on insects as soon as they hatch, although they stay near the female for protection.

Although most mallard drakes would normally leave the hen after she has laid her eggs, very few like this one are known to remain longer to become the leader of the family.

When they pair off with mating partners, often one or several drakes will end up "left out". This group will sometimes target an isolated female duck: chasing, pestering and pecking at her until she weakens (a phenomenon referred to by researchers as rape flight), at which point each male will take turns copulating with the female. Male mallards will also occasionally chase other males in the same way. (In one documented case, a male mallard copulated with another male he was chasing after said male had been killed when he flew into a glass window.)[6]

Taxonomy and evolution

Mallard eggs and a nest.

The mallard is the ancestor of almost all of the varieties of domestic ducks. Domestic ducks belong to the subfamily Anatinae of the waterfowl family Anatidae. The wild mallard and Muscovy duck (Cairina moschata) are believed to be the ancestors of all domestic ducks.[7]

Mallards frequently interbreed with their closest relatives in the genus Anas, such as the American Black Duck, and also with species more distantly related, for example the Northern Pintail, leading to various hybrids that may be fully fertile. This is quite unusual among different species, and apparently has its reasons in the fact that the mallard evolved very rapidly and not too long ago, during the Late Pleistocene only. The distinct lineages of this radiation are usually kept separate due to non-overlapping ranges and behavioural cues, but are still not fully genetically incompatible. Mallards and their domesticated conspecifics are, of course, also fully interfertile.

Iridescent blue-black-white speculum feathers of male

Mallards appear to be closer to their Indo-Pacific relatives than to their American ones judging from biogeography. Considering mtDNA D-loop sequence data,[8] they may have evolved more probably than not in the general area of Siberia; mallard bones rather abruptly appear in food remains of ancient humans and other deposits of fossil bones in Europe, without a good candidate for a local predecessor species. The large ice age paleosubspecies which made up at least the European and W Asian populations during the Pleistocene has been named Anas platyrhynchos palaeoboschas.

Haplotypes typical of American mallard relatives and Spotbills can be found in mallards around the Bering Sea.[9] The Aleutian Islands turned out to hold a population of mallards that appear to be evolving towards a subspecies as gene flow with other populations is very limited.[8]

The size of the mallard varies clinally, and birds from Greenland, although larger than birds further south, have smaller bills and are stockier. It is sometimes separated as subspecies Greenland Mallard (A. p. conboschas).

Ecology and conservation

The last male Mariana Mallard.

The release of feral mallards in areas where they are not native sometimes creates problems through interbreeding with indigenous waterfowl. These non-migratory mallards interbreed with indigenous wild ducks from local populations of closely related species through genetic pollution by producing fertile offspring. Complete hybridization of various species of wild ducks gene pools could result in the extinction of many indigenous waterfowl. The wild mallard itself is the ancestor of most domestic ducks and its naturally evolved wild gene pool gets genetically polluted in turn by the domesticated and feral populations.[10][11][12]

The mallard is considered an invasive species in New Zealand. There, and elsewhere, mallards are spreading with increasing urbanization and hybridizing with local relatives.[13] Over time, a continuum of hybrids ranging between almost typical examples of either species will develop; the speciation process beginning to reverse itself.[14] This has created conservation concerns for relatives of the mallard, such as the Hawaiian Duck,[15] the A. s. superciliosa subspecies of the Pacific Black Duck,[16] the American Black Duck,[17] the Florida Duck,[18] Meller's Duck,[19] the Yellow-billed Duck,[14] and the Mexican Duck,[20] in the latter case even leading to a dispute whether these birds should be considered a species[21] (and thus entitled to more conservation research and funding) or included in the mallard.

Mallards are also causing severe "genetic pollution" of South Africa's biodiversity by breeding with endemic ducks, although the Agreement on the Conservation of African-Eurasian Migratory Waterbirds applies to the mallard. The hybrids of mallard and the Yellow-billed Duck are fertile and can produce more hybrid offspring. If this continues, only hybrids will occur and in the long term this will result in the extinction of various indigenous waterfowl. The mallard duck can cross breed with 63 other species and is posing a severe threat to the genetic integrity of indigenous waterfowl. Mallards and their hybrids compete with indigenous birds for resources such as food, nest sites and roosting sites.[12]

The Chinese Spotbill is currently introgressing into the mallard populations of the Primorsky Krai, possibly due to habitat changes from global warming.[22] The Mariana Mallard was a resident allopatric population—in most respects a good species—apparently initially derived from mallard-Pacific Black Duck hybrids;[23] unfortunately, it became extinct in the 1980s. In addition, feral domestic ducks interbreeding with mallards have led to a size increase—especially in drakes—in most mallards in urban areas. Rape flights between normal-sized females and such stronger males are liable to end with the female being drowned by the males' combined weight.

Female with ducklings

The Laysan Duck is an insular relative of the mallard with a very small and fluctuating population. Mallards sometimes arrive on its island home during migration, and can be expected to occasionally have remained and hybridized with Laysan Ducks as long as these species exist. But these hybrids are less well adapted to the peculiar ecological conditions of Laysan Island than the local ducks, and thus have lower fitness, and furthermore, there were—apart from a brief time in the early 20th century when the Laysan Duck was almost extinct—always much more Laysan Ducks than stray mallards. Thus, in this case, the hybrid lineages would rapidly fail.

In the cases mentioned above, however, ecological changes and hunting have led to a decline of local species; for example, the New Zealand Grey Duck population declined drastically due to overhunting in the mid-20th century.[24] In the Hawaiian Duck, it seems that hybrid offspring are less well-adapted to native habitat and that utilizing them in reintroduction projects makes these less than successful.[25] In conclusion, the crucial point underlying the problems of mallards "hybridizing away" relatives is far less a consequence of mallards spreading, but of local ducks declining; allopatric speciation and isolating behaviour have produced today's diversity of mallard-like ducks despite the fact that in most if not all of these populations, hybridization must have occurred to some extent.

In culture

The mallard is depicted in a marginal decoration of the 15th century English illuminated manuscript the Sherborne Missal.[26]

Footnotes

  1. ↑ Etymology: Ancient Greek for "flat-billed duck" [1]
  2. ↑ Phillips, J. C. 1915. Experimental studies of hybridization among ducks and pheasants. Journal of Experimental Zoology 18:69-112.
  3. ↑ Rogers (2001)
  4. ↑ "Baltimore Bird Club. Group Name for Birds: A Partial List". http://baltimorebirdclub.org/gnlist.html. Retrieved 2007-06-03. 
  5. ↑ Herrera et al. (2006)
  6. ↑ Moeliker (2001). This paper was awarded with an Ig Nobel Prize in 2003 (MacLeod 2005).
  7. ↑ Anas platyrhynchos, Domestic Duck; DigiMorph Staff - The University of Texas at Austin
  8. ↑ 8.0 8.1 Kulikova et al. (2005)
  9. ↑ Kulikova et al. (2004, 2005)
  10. ↑ Mottled Ducks : The Problem : Hybridization; Florida Fish and Wildlife Conservation Commission, MyFWC.com
  11. ↑ Environmental assessment for control of free-ranging resident mallards in Florida, May 2002, Contact: Frank Bowers, U.S. Fish and Wildlife Service
  12. ↑ 12.0 12.1 Invasive Alien Bird Species Pose A Threat, Kruger National Park, Siyabona Africa Travel (Pty) Ltd - South Africa Safari Travel Specialist
  13. ↑ Rhymer & Simberloff (1996)
  14. ↑ 14.0 14.1 Rhymer (2006)
  15. ↑ Griffin et al. (1989), Rhymer & Simberloff (1996)
  16. ↑ Gillespie (1985), Rhymer et al. (1994), Rhymer & Simberloff (1996), Williams & Basse (2006).
  17. ↑ Johnsgard (1967), Avise et al. (1990), Rhymer & Simberloff (1996), Mank et al. (2004).
  18. ↑ Mazourek & Gray (1994), Rhymer & Simberloff (1996), McCracken et al. (2001).
  19. ↑ Young & Rhymer (1998)
  20. ↑ Rhymer & Simberloff (1996), McCracken et al. (2001)
  21. ↑ See AOU (1983)
  22. ↑ Kulikova et al. (2004)
  23. ↑ Yamashina (1948)
  24. ↑ Williams & Basse 2006
  25. ↑ Rhymer & Simberloff (1996), see also Kirby et al. (2004)
  26. ↑ Clark, Kenneth (1977). Animals and Men. London: Thames and Hudson. pp. 107. ISBN 0-500-23257-1. 

References

  • American Ornithologists' Union (AOU) (1983): Check-list of North American Birds (6th edition). American Ornithologists' Union, Washington, DC.
  • Avise, John C.; Ankney, C. Davison & Nelson, William S. (1990): Mitochondrial Gene Trees and the Evolutionary Relationship of Mallard and Black Ducks. Evolution 44(4): 1109-1119. doi:10.2307/2409570 (HTML abstract and first page image)
  • Bagemihl, Bruce (1999): Biological Exuberance: Animal Homosexuality and Natural Diversity: 479-481. St. Martin's Press. ISBN 0312192398
  • BirdLife International (2004). Anas platyrhynchos. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes justification for why this species is of least concern
  • Gillespie, Grant D. (1985): Hybridization, introgression, and morphometric differentiation between Mallard (Anas platyrhynchos) and Grey Duck (Anas superciliosa) in Otago, New Zealand. Auk 102 (3): 459-469. PDF fulltext
  • Griffin, C.R.; Shallenberger, F.J. & Fefer, S.I. (1989): Hawaii's endangered waterbirds: a resource management challenge. In: Sharitz, R.R. & Gibbons, I.W. (eds.): Proceedings of Freshwater Wetlands and Wildlife Symposium: 155-169. Savannah River Ecology Lab, Aiken, South Carolina.
  • Herrera, Néstor; Rivera, Roberto; Ibarra Portillo, Ricardo & Rodríguez, Wilfredo (2006): Nuevos registros para la avifauna de El Salvador. ["New records for the avifauna of El Salvador"]. Boletín de la Sociedad Antioqueña de Ornitología 16(2): 1-19. [Spanish with English abstract] PDF fulltext
  • Johnsgard, Paul A. (1967): Sympatry Changes and Hybridization Incidence in Mallards and Black Ducks. American Midland Naturalist 77(1): 51-63. doi:10.2307/2423425 (HTML abstract and first page image)
  • Johnson, Kevin P. & Sorenson, Michael D. (1999): Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence. Auk 116 (3): 792–805. PDF fulltext
  • Kirby, Ronald E.; Sargeant, Glen A. & Shutler, Dave (2004): Haldane's rule and American black duck × mallard hybridization. Canadian Journal of Zoology 82(11): 1827–1831. doi:10.1139/z04-169 (HTML abstract)
  • Kulikova, Irina V.; Zhuravlev, Yury N. & McCracken, Kevin G. (2004): Asymmetric hybridization and sex-biased gene flow between Eastern Spot-billed Ducks (Anas zonorhyncha) and Mallards (A. platyrhynchos) in the Russian Far East. Auk 121 (3): 930-949. [English with Russian abstract] DOI: 10.1642/0004-8038(2004)121[0930:AHASGF]2.0.CO;2 PDF fulltext
  • Kulikova, Irina V.; Drovetski, S.V.; Gibson, D.D.; Harrigan, R.J.; Rohwer, S.; Sorenson, Michael D.; Winker, K.; Zhuravlev, Yury N. & McCracken, Kevin G. (2005): Phylogeography of the Mallard (Anas platyrhynchos): Hybridization, dispersal, and lineage sorting contribute to complex geographic structure. Auk 122 (3): 949-965. [English with Russian abstract] DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2 PDF fulltext. Erratum: Auk 122 (4): 1309. DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2
  • MacLeod, Donald (2005): Necrophilia among ducks ruffles research feathers. Education Guardian (March 8). Retrieved 2006-DEC-09.
  • Mank, Judith E.; Carlson, John E. & Brittingham, Margaret C. (2004): A century of hybridization: Decreasing genetic distance between American black ducks and mallards. Conservation Genetics 5(3): 395–403. doi:10.1023/B:COGE.0000031139.55389.b1 (HTML abstract)
  • Mazourek, J.C. & Gray, P.N. (1994): The Florida duck or the mallard? Florida Wildlife 48 (3): 29-31. DOC fulltext
  • McCracken, Kevin G.; Johnson, William P. & Sheldon, Frederick H. (2001): Molecular population genetics, phylogeography, and conservation biology of the mottled duck (Anas fulvigula). Conservation Genetics 2 (2): 87–102. doi:10.1023/A:1011858312115 PDF fulltext
  • Moeliker, C. W. "Kees" (2001): The first case of homosexual necrophilia in the Mallard Anas platyrhynchos (Aves: Anatidae). Deinsea 8: 243-247. PDF fulltext
  • Rhymer, Judith M. (2006): Extinction by hybridization and introgression in anatine ducks. Acta Zoologica Sinica 52(Supplement): 583–585. PDF fulltext
  • Rhymer, Judith M. & Simberloff, Daniel (1996): Extinction by hybridization and introgression. Annu. Rev. Ecol. Syst. 27: 83-109. doi:10.1146/annurev.ecolsys.27.1.83 (HTML abstract)
  • Rhymer, Judith M.; Williams, Murray J. & Braun, Michael J (1994). Mitochondrial analysis of gene flow between New Zealand Mallards (Anas platyrhynchos) and Grey Ducks (A. superciliosa). Auk 111 (4): 970–978. PDF fulltext
  • Rogers, D. (2001): Animal Diversity Web: Anas platyrhynchos. Retrieved 2006-DEC-08.
  • Williams, Murray & Basse, Britta (2006): Indigenous gray ducks, Anas superciliosa, and introduced mallards, A. platyrhynchos, in New Zealand: processes and outcome of a deliberate encounter. Acta Zoologica Sinica 52(Supplement): 579–582. PDF fulltext
  • Yamashina, Y. (1948): Notes on the Marianas mallard. Pacific Science 2: 121-124.
  • Young, H. Glyn & Rhymer, Judith M. (1998): Meller's duck: A threatened species receives recognition at last. Biodiversity and Conservation 7: 1313-1323. doi:10.1023/A:1008843815676

External links

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See also
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1 Rarely shot due to declining numbers.
2 England and Wales only; protected Scotland.